The mother of a New York civil-rights worker slain with two others in Mississippi more than 40 years ago said yesterday that if she met the reputed Ku Klux Klansman just indicted for their killings, she would ask him what went through his mind that night to help him unburden his soul.

“Would it help him to open up to me? I would like him to relieve himself,” Carolyn Goodman said. “I would ask him what was in his mind . . . what moved him to murder three innocent men.”

The 89-year-old mother of Andrew Goodman remained resolute, however, that justice would be done.

“There was always a sense it was going to happen,” she said in her Upper West Side apartment, surrounded by pictures and paintings of her son.

Goodman spoke shortly after Edgar Ray Killen, 79, pleaded not guilty to murder charges in a Philadelphia, Miss., courtroom. He is the only person to ever be criminally indicted in the infamous 1964 killings, which were depicted in the 1988 movie “Mississippi Burning.”

Killen, handcuffed and dressed in an orange prison jumpsuit, said he couldn’t afford a lawyer and was then led off to jail, pending a bail hearing.

Underscoring the emotion behind the case, the courthouse was cleared soon after the hearing, when authorities received a bomb threat, although none was found.

Killen is charged in the deaths of James Chaney, a 21-year-old black man from Mississippi, and two white New Yorkers, Goodman, 20, and Michael Schwerner, 24.

The three were beaten and shot to death on a desolate stretch of dirt road after allegedly being stopped by Klansmen. Their bodies were buried in a dam a few miles away.

District Attorney Mark Duncan said that while the grand-jury indictment came quickly, “it hadn’t been fast for us. We’ve been investigating the case for several years now. It just finally got to the point where we felt like we had done all that we can do.”

Not all were pleased with the investigation.

Chaney’s younger brother, Ben, called it a sham that may target one or two unrepentant Klansmen – but spare the wealthy and influential whites he claims were behind the slayings.

In 1967, Killen and 18 other men were tried on federal civil-rights violations. Seven were convicted, but Killen’s trial ended in a hung jury. With Post Wire Services